Magnetic lock and key

ABSTRACT

A lock for operation by a magnetic key has a magnetic locking element (47) which moves in aligned, longitudinal grooves formed in inner (10) and outer (18) members of the lock. When the locking element is aligned with a transverse channel (57) in the inner member, limited relative rotation of the members can occur.

This invention relates to a lock and key, there being associated withthe key a permanent magnetic field and the lock comprising at least onemagnetic locking element which can be moved from a locking position to areleasing position by the magnetic field of the key, when the key isapplied to the lock.

A magnetic lock and key are described in U.S. Pat. No. 2,177,996. Thislock comprises a hollow plug arranged for rotation within a sleeve.Axially extending grooves formed in the plug and sleeve collectivelydefine a path along which a magnetic ball can be moved by the magneticfield of the key from a locking position to a releasing position. In thelocking position, the ball is engageable with abutment surfaces atopposite sides of its path, these surfaces being formed on the plug andsleeve respectively, so that relative rotation of the plug and sleeve isrestrained. In the sleeve, there is formed a circumferentially extendinggroove which communicates with the axially extending groove. When theball is in its releasing position, it is aligned with thecircumferentially extending groove so that relative rotation of the plugand sleeve is possible. A second magnetic ball is disposed in a similarpair of axially extending grooves which communicate with thecircumferentially extending groove. The possibility of providing furthermagnetic locking balls is mentioned.

One disadvantage of the lock described in the aforesaid U.S. patent isthat manufacture of the lock becomes unduly complex if the number ofmagnetic elements is increased. In order to provide a sufficiently largenumber of different locks and keys to ensure proper security, a numberof locking elements exceeding two is required. The U.S. patent proposesthat the number of different locks and keys which can be produced shouldbe increased by varying the position relative to the grooves of adriving lug of the key. However, this simple mechanical expedient doesnot provide adequate security.

According to a first aspect of the present invention, there is provideda lock comprising an inner member, a hollow outer member in which theinner member is mounted and a magnetic element, wherein the inner andouter members collectively define a path to which the magnetic elementis confined and along which the magnetic element can move between areleasing position and a locking position, the inner and outer membershave respective abutment surfaces facing in opposite directionstransverse to the length of said path and disposed at opposite sides ofsaid path, said abutment surfaces are engageable concurrently with themagnetic element except when the magnetic element occupies its releasingposition, whereby relative movement of the inner and outer members insaid directions is restricted or prevented by engagement of the magneticelement with the abutment surface except when the magnetic elementoccupies its releasing position and wherein there is in the abutmentsurface of the inner member an opening which a part of the magneticelement can enter when the element is in its releasing position.

According to a second aspect of the invention, there is provided a lockcomprising an inner member, a hollow outer member in which the innermember is mounted for turning relative thereto about an axis, a housingin which the outer member is received, an element which is movable by akey between a locking position in which it prevents relative turning ofsaid members about the axis and a releasing position in which it permitsat least limited relative turning of the members, and a stop elementwhich releasably prevents turning of the outer member relative to thehousing until the inner member has been turned through a predeterminedangle to effect release of the outer member for turning with the innermember.

According to a third aspect of the invention, there is provided a lockcomprising an inner member, a hollow outer member in which the innermember is mounted and a magnetic element, wherein the inner and outermembers collectively define a path to which the magnetic element isconfined and along which the magnetic element can move between areleasing position and a locking position, the inner and outer membershave respective abutment surfaces facing in opposite directionstransverse to the length of said path and disposed at opposite sides ofsaid path, said abutment surfaces are engageable concurrently with themagnetic element except when the magnetic element occupies its releasingposition, whereby relative movement of the inner and outer members insaid directions is restricted or prevented by engagement of the magneticelement with the abutment surfaces except when the magnetic elementoccupies its releasing position, the inner and outer members are eachformed with a respective groove, respective parts of said groovescollectively form said path and wherein one of the inner and outermembers has an element extending across its groove between the endsthereof to limit travel of the magnetic element along the groove.

According to a fourth aspect of the invention, there is provided a lockcomprising a tubular inner element, a sleeve in which the inner elementis mounted and a magnetic element, wherein the inner element and sleevecollectively define a path to which the magnetic element is confined andalong which the magnetic element can move between a releasing positionand a locking position, the inner element and the sleeve have respectiveabutment surfaces facing in opposite directions transverse to the lengthof said path and disposed at opposite sides of said path, said abutmentsurfaces are engageable concurrently with the magnetic element exceptwhen the magnetic element occupies its releasing position, wherebyrelative movement of the inner element and sleeve in said directions isrestricted or prevented by engagement of the magnetic element with theabutment surfaces except when the magnetic element occupies itsreleasing position and wherein the inner element and the sleeve haverespective channels extending along their entire lengths and eachcontaining a respective part of the magnetic element, the abutmentsurfaces being boundary surfaces of the channels.

According to a fifth aspect of the invention, there is provided a lockand key whereof the lock has an operating member which can be turnedabout an axis when the key is applied to the lock, said operating membercan be locked in a selected one of a plurality of alternative positionsupon withdrawal of the key from the lock and the lock includes akey-retaining member which also turns about the axis during operation ofthe lock and is adapted to retain the key except when the operatingmember is in one of said alternative positions. Because thekey-retaining member participates in turning about the axis, it is notnecessary to modify the shape of the key-retaining member according tothe number of and relationship between the alternative positions inwhich the operating member can be locked.

According to a still further aspect of the invention, there is provideda key with which there is associated a permanent magnetic field, the keycomprising a shank formed at least partly of magnetic material andhaving a pole face which has a longer dimension extending along theshank and a shorter dimension extending around the shank.

There is also provided in accordance with the invention the combinationcomprising a lock according to any one of the first, second, third andfourth aspects of the invention and a key having a shank which presentsa plurality of magnetic poles and is adapted to transmit torque to atleast one of the inner and outer members of the lock.

One example of a lock and key embodying each aspect of the inventionwill now be described, with reference to the accompanying drawingswherein:

FIG. 1 shows an end view of the lock, the key being absent from thelock;

FIG. 2 shows an opposite end view of the lock;

FIG. 3 shows a cross-section on the line III--III of FIG. 1, togetherwith a key of which the shank is present in the lock;

FIG. 4 shows a cross-section on the line IV--IV of the lock and key,prior to rotation of the key;

FIG. 5 shows a cross-section on the line IV--IV of FIG. 3 after the keyhas been rotated through an angle of 30°;

FIG. 6 shows a cross-section on the line VI--VI of FIG. 3, prior toturning of the key;

FIG. 7 shows a cross-section on the line VI--VI after the key has beenrotated through an angle of 30°; and

FIG. 8 shows a cross-section of the lock on the line VIII--VIII of FIG.3.

The lock illustrated in the accompanying drawings comprises an innermember 10 of generally cylindrical form having a longitudinal axis 11about which the inner member is turned by means of a key 12 duringoperation of the lock. On an end portion 13 of the inner member, calledherein the rear end portion, there is formed a pair of flats 14 whichengage an operating arm 15 within a non-circular opening of the arm. Thearm is trapped on the inner member between a circlip 16 and a nut 17.The arm 15 is used to control a device which is to be controlled by thelock. For example, the arm itself may be a latch. Alternatively, theremay be formed on the arm a cam surface which co-operates with an element(not shown) controlled by the lock.

The lock further comprises a hollow outer member 18, also of generallycylindrical form, within which the inner member 10 is mounted. The outermember is concentric with the inner member and is a sliding fit on theinner member.

The outer member 18 is disposed within a housing 19, relative to whichthe outer member can turn about the axis 11 when the proper key is usedto operate the lock. The shape of the housing may be selected accordingto the intended use of the lock. As illustrated, the housing may beformed in a plurality of parts, at least some of which may be providedwith screw threads to enable the parts of the housing to be releasablysecured together. In the example illustrated, a front part 20 of thehousing extends through an opening in a mounting plate 21 and is securedtherein by a nut 22 screwed onto the front housing part. The entirehousing will normally be fixed during use of the lock.

A stop element 23 is provided for releasably preventing turning of theouter member 18 relative to the housing 19 until the inner member 10 hasbeen turned by means of the key 12 through a predetermined angle toeffect release of the outer member. The stop element is in the form of abolt having a central opening through which the rear end portion 13 ofthe inner member protrudes. The bolt is held against a rear end face 24of the outer member 18 by a bolt carrier 25. The bolt carrier is ofhollow, generally cylindrical form having one end wall and an externaldiameter equal to that of the outer member 18. The bolt carrier hasthree limbs 26, 27, 28 which project from the end wall of the carrier inthe forward direction through the central aperture of the bolt. Fivegrooves are formed in the external surface of the inner member 10, eachof these grooves being rectilinear, parallel to the axis 11 andextending along the entire length of the inner member. The limbs 26, 27and 28 of the bolt carrier engage in respective ones of these groovesindicated by the reference numerals 29, 30 and 31. The bolt carrier isthereby constrained to turn about the axis 11 with the inner memberrelative to the bolt and the outer member.

There is formed in the wall of the outer member 18 adjacent to the rearend thereof an opening 32. Openings having dimensions extendingcircumferentially of the axis 11 similar to the corresponding dimensionof the opening 32 are formed in a rear part 33 of the housing 19adjacent to a rear wall 34 of the housing. In the example illustrated,there are four of these openings in the housing identified by thereference numerals 35 to 38. The bolt 23 has a nose 39 which canprotrude through the opening 32 into any selected one of the openings 35to 38 and thereby restrain turning of the outer member 18 about the axis11 relative to the housing. The bolt is urged into the active positionillustrated in FIG. 3 by a leaf spring 40 having a mid portion whichbears against the bolt and end portions which bear against the internalface of the outer member 18. Engagement of the nose 39 of the bolt inthe opening 32 prevents turning of the bolt relative to the outermember.

From the nose 39 there projects into the central opening of the bolt 23an abutment 41 of the bolt. When the key is absent from the lock, theabutment 41 is aligned with the limb 27 of the bolt carrier 25 as shownin FIG. 4 so that complete withdrawal of the bolt from the opening ofthe housing is prevented by engagement of the abutment 41 with the limb27 which constitutes an abutment of the bolt carrier.

If the key 12 is inserted into the inner member 10 and the key and innermember are then turned in either direction about the axis 11, the limb27 is moved out of alignment with the abutment 41 so that the nose 39 ofthe bolt can move towards the axis 11. Turning of the inner member ineither direction also brings one or other of the limbs 26 and 28 intoengagement with a respective surface 42 or 43 on the bolt which facesgenerally in a direction away from the leaf spring 40 and towards thenose 39. Further turning of the inner member causes the bolt to slidebetween the end face 24 of the outer member and the end wall of the boltcarrier in a direction transverse to the axis 11 until the nose 39 issubstantially withdrawn from the opening of the housing. As shown, thenose 39 may be provided with a rounded tip which will automatically beforced out of the opening in the housing upon rotation of the bolt andouter member relative to the housing, provided the nose is substantiallywithdrawn from the opening of the housing before rotation of the outermember commences. Thus, by turning of the inner member 10 the bolt canbe moved to the releasing position illustrated in FIG. 5 in which it nolonger restrains rotation of the outer member 18.

The outer member 18 consists of a tubular element 44 and an end cap 45secured on the front end of the element 44. In the internal surface ofthe element 44, there is formed a number of grooves equal to the numberof grooves provided in the external surface of the inner member 10. Thecircumferential extent and spacing between the grooves 46 of the outermember are the same as those of the grooves of the inner member so thateach of the grooves 46 can be aligned with a corresponding groove of theinner member. The grooves 46 also extend along the entire length of theelement 44 and are parallel to the axis 11. Three magnetic elements 47,48 and 49 are each disposed partly in the groove 30 of the inner memberand partly in the corresponding groove 46 of the outer member. In theparticular example illustrated, each magnetic element is in the form ofa hollow cylinder having flat end faces which are engageable withboundary surfaces of the grooves 30 and 46. In the example illustrated,each of these grooves has a transverse cross-section of rectangularshape with flat abutment surfaces at opposite sides of the grooves.

The groove 30 extends through a major part of the thickness of the innermember 10, almost to the central bore 50 thereof. There are also formedin the outer surface of the inner member 10 a plurality of relativelyshallow circumferentially extending grooves 51 containing respectiverings 52 to 55. The ring 52 lies adjacent to the rear end of the innermember. The rings 53 to 55 lie between the ends of the groove 30 and arespaced apart from each other along the axis 11. As shown in FIG. 3, themagnetic elements 47 to 49 lie between respective different pairs of therings 52 to 55 so that travel of the magnetic elements along the groove30 is limited to prevent two or more magnetic elements occupying thesame part of the groove. In the absence of the key, each magneticelement is free to move along a respective path defined collectively bythe boundary surfaces of the grooves 30 and 46, these paths beingcolinear and parallel to the axis 11.

In the abutment surfaces at opposite sides of the groove 30, there areformed openings 56 which are sufficiently large to receive that part ofa magnetic element 47 to 49 which is normally disposed in the groove 30.In the example illustrated, there is in each abutment surface a singleopening for the element 47, a single opening for the element 48 and twoaxially spaced openings for the element 49. The openings 56 are formedby the provision of transversely extending channels in the externalsurface of the inner member 10.

The boundary surface of each transverse channel 57 which faces away fromthe axis 11, that is the base of the channel, is such that there can bedrawn on the base of the channel a rectilinear line transverse to thelength of the groove 30. At the position where a transverse channel 57intersects the groove 30, the depth of the transverse channel is equalto that of the groove. The depth of the transverse channel decreasesgradually in both directions away from the groove 30 until thetransverse channel runs out onto the external surface of the innermember. In the particular example illustrated, the base of eachtransverse channel is flat.

When any one of the magnetic elements 47, 48 and 49 is not aligned witha corresponding one of the transverse channels 57, that element is saidto be in a locking position and, by engagement with opposed abutmentsurfaces of the inner and outer members, it prevents or restrictsturning of the inner member about the axis 11 relative to the outermember. When the key is absent from the lock, at least some and usuallyall of the magnetic elements will occupy locking positions.

It will be noted that the depth of the groove 30 significantly exceedsone half of the corresponding dimension of the magnetic elements andthat the depth of the grooves 46 is similar to that of the groove 30.However, the depth of these grooves is significantly less than thecorresponding dimension of the magnetic elements. There is associatedwith the key 12 a permanent magnetic field such that, when a shank 58 ofthe key is introduced into the central bore 50 of the inner member, eachof the magnetic elements is biased by the magnetic field into areleasing position where it is aligned with a respective one of thetransverse channels 57. Thus, the magnetic elements are no longerengaged between oppositely facing abutment surfaces and the inner membercan be turned about the axis 11 in either direction relative to theouter member 18. Since a part of each magnetic element remains in thegroove 46, such turning causes each magnetic element to move along thebase of the corresponding transverse channel and therefore to movefurther away from the axis 11. Before such movement is interrupted byengagement of the magnetic elements with a radially inwardly facingsurface of the outer member, the outer member itself is freed forturning movement with the inner member by retraction of the nose 39 ofthe bolt from the opening in the housing 19. Continued turning of theinner member 10 is then accompanied by turning of the outer memberrelative to the housing. The inner member is turned sufficiently tobring about operation of an associated device by means of the arm 15.

The arm 15 can be locked in a selected angular position by turning theinner member 10 in the reverse direction relative to the outer member 18whilst the nose 39 of the bolt is aligned with a selected one of theopenings 35 to 38 in the housing 19. Such alignment is indicated to auser by noticably increased resistance to turning of the inner member 10which is necessary to force the rounded tip of the nose 39 out of one ofthe openings in the housing, against the action of the spring 40. Itwill be understood that reverse rotation of the inner member 10 relativeto the outer member 18 causes the magnetic elements 47, 48 and 49 tomove along their respective transverse channels 57 into alignment withthe groove 30 once more. Withdrawal of the key then displaces themagnetic elements along their respective paths of movement into lockingpositions.

In the end cap 45, there are formed three recesses 59 having open sidesfacing along the axis 11 towards the inner member 10. In each of theserecesses there is disposed a freely rotatable ball 60 of hardened steel.These balls prevent the drilling away of the end cap so that the innermember 10 can be withdrawn from the outer member 18. The end cap alsodefines a non-circular opening 61 through which the key shank can beintroduced into the bore 50 of the inner member. The opening 61comprises a circular portion having the same diameter as, and beingaligned with, the bore 50 and a rectangular extension 62 of the circularportion. The shank 58 of the key is of generally cylindrical form buthas, adjacent to a handle of the key, a radially projecting lug 63having dimensions such that it can pass through the extension 62 of theopening in the end cap. Immediately adjacent to the opening 61 andbetween that opening and the inner member 10, there is in the end cap 45an arcuate recess 64 which accommodates the lug 63 of the key when thekey is turned relative to the outer member 18 through an angle of 30° ineither direction after the lug has passed through the opening 61. Afterthe key has been turned through an angle of 30° relative to the outermember, torque can be transmitted from the key to the outer member byengagement of the lug 63 with boundary surfaces of the recess 64.

The lug 63 also transmits torque to the inner member 10 by engaging in arecess 65 at the front end thereof. There is only a small clearancebetween the lug 63 and the boundary surfaces of the recess 65 so that nosignificant turning of the key relative to the inner member 10 ispermitted. It will be seen that portions of the end cap 45 bordering therectangular extension 62 of the opening therein trap the key in the bore50 of the inner member whenever the nose 39 of the bolt is withdrawn orsubstantially withdrawn from the openings 35 to 38 of the housing. Onlywhen the nose 39 is engaged in an opening of the housing can be the limb27 be moved into alignment with the abutment 41 to align the lug 63 withthe extension 62 of the opening in the end cap and thereby permitextraction of the key from the lock.

The end cap 45 may include flaps 66 which substantially close theopenings of the end cap when the key is absent from the lock. The endcap is preferably formed of a resilient plastics material by a mouldingprocess.

The inner member 10 and the tubular element 44 of the outer member arepreferably formed of a non-magnetic metal, for example aluminium orbrass. Since the groove 30 and other grooves of the inner member and thegrooves 46 of the outer member are rectilinear and extend along theentire lengths of the inner member and element 44 respectively, thesegrooves can conveniently be formed by an extrusion process. This has theadvantage that smooth abutment surfaces on the inner and outer memberscan be achieved without careful machining of the inner and outermembers. The other grooves and openings in the inner and outer membersare formed by machining extruded tubular workpieces. It will be notedthat each transverse channel 57 can be formed by a single straight cutacross the inner member 10.

The inner member 10 is preferably formed by extrusion with a centralopening 67 of smaller diameter than the bore 50, the bore subsequentlybeing formed in the inner member by machining. It will be noted fromFIG. 3 that the bore 50 does not extend into the rear end portion 13 ofthe inner member.

The key shank 58 is provided with magnetic pole faces at positionscorresponding to respective paths of the magnetic elements. Each poleface has a length, measured along the axis 11, which exceeds its width,measured circumferentially of the axis 11 and a maximum flux density ata position corresponding to the releasing position of the associatedmagnetic element. In the example illustrated, the magnetic element 49has two releasing positions and is moved into one of these positions bya master key and into the other position by another key.

It will be understood that the number of magnetic elements in eachgroove of the inner member can be varied. In the particular exampledescribed, only one groove of the inner member contains magneticelements but generally more than one groove will contain at least onemagnetic element. Locks will also differ one from the other in respectof the relation between the releasing position of each magnetic elementand the ends of its path of movement.

By appropriate choice of the relative positions of the paths of themagnetic elements, the magnetic pole faces of the key can be spaced wellapart. This facilitates the establishment of high flux densities at themagnetic poles so that reliable operation of the lock by the key isassured even under adverse conditions.

I claim:
 1. A lock comprising an inner member, a hollow outer member inwhich the inner member is mounted and a plurality of magnetic elements,wherein the inner and outer members collectively define respective pathsto which the magnetic elements are confined and along which the magneticelements can move between respective releasing positions and respectivelocking positions, the inner and outer members have, for each path,respective abutment surfaces facing in opposite directions transverse tothe length of the path and disposed at opposite sides of the path andsaid abutment surfaces are engageable concurrently with respective onesof the magnetic elements when the magnetic elements occupy their lockingpositions, whereby relative movement of the inner and outer members insaid directions is restricted or prevented by engagement of the magneticelements with the abutment surfaces except when the magnetic elementsoccupy their releasing positions, characterised in that there are in theabutment surfaces of the inner member openings corresponding torespective ones of the magnetic elements and each of which openings apart of the corresponding magnetic element can enter when the element isin its releasing position and in that means is provided for preventingmovement of one of said magnetic elements into the opening correspondingto another of the magnetic elements.
 2. A lock according to claim 1wherein said openings are formed by the intersection of respectivetransverse channels and said paths, one boundary of each transversechannel being a respective surface of the inner member which facestowards the outer member and contains a rectilinear line transverse tothe corresponding path.
 3. A lock according to claim 2 wherein eachtransverse channel extends from the corresponding path in oppositedirections.
 4. A lock according to claim 2 wherein said surface of eachtransverse channel is flat.
 5. A lock according to claim 1 wherein, whenthe locking element is in its releasing position, the inner and outermembers can undergo limited relative rotation about an axis parallel tothe length of said path.
 6. A lock comprising an inner member, a hollowouter member in which the inner member is mounted, a housing for theouter member and a plurality of magnetic elements, wherein the inner andouter members collectively define respective paths to which the magneticelements are confined and along which the magnetic elements can movebetween respective releasing positions and respective locking positions,the inner and outer members have, for each path, respective abutmentsurfaces facing in opposite directions transverse to the length of thepath and disposed at opposite sides of the path and said abutmentsurfaces are engageable concurrently with respective ones of themagnetic elements when the magnetic elements occupy their lockingpositions, whereby relative movement of the inner and outer members insaid directions is restricted or prevented by engagement of the magneticelements with the abutment surfaces except when the magnetic elementsoccupy their releasing positions, characterised in that there are in theabutment surfaces of the inner member openings corresponding torespective ones of the magnetic elements and each of which of openings apart of the corresponding magnetic elements can enter when the elementis in its releasing position, in that means is provided for preventingmovement of one of said magnetic elements into the opening correspondingto another of the magnetic elements, in that, when the locking elementsare in their releasing positions, the inner and outer members canundergo limited rotation about an axis parallel to the lengths of saidpaths and in that there is provided a stop element which releasablyprevents turning of the outer member relative to the housing until theinner member has been turned through a predetermined angle to effectrelease of the outer member for turning with the inner member.
 7. A lockaccording to claim 6 wherein the stop element is a slidable bolt whichis movable transversely of the axis between an active position and aninactive position, in its active position the bolt engages in respectiveopenings in the outer member and in the housing and the inner member hasan abutment which, when the locking element is in its locking position,is engageable with the bolt to prevent movement of the bolt from itsactive position to is inactive position.
 8. A lock according to claim 7wherein the housing has a plurality of openings, in any selected one ofwhich the bolt can engage to restrain turning of the outer memberrelative to the housing.
 9. A lock according to claim 1 wherein theinner member has a bore to receive a shank of the key, the outer memberdefines a noncircular aperture through which the key shank can beintroduced into the bore of the inner member and there is adjacent tothe aperture a space which can accommodate a non-circular part of thekey shank complementary to said aperture after such part has been passedthrough the aperture and then turned about the axis to trap the keyshank in the outer member.
 10. A lock according to claim 1 wherein atleast one of said inner and outer members is formed by an extrusionprocess with respective channels each extending from one end of themember to the other end and a part of the magnetic element is receivedin the channel.
 11. A lock according to claim 1 wherein said inner andouter members are each formed with a respective groove, respective partsof said grooves collectively form the path for at least one magneticelement and wherein one of the inner and outer members has an elementextending across its groove between the ends thereof to limit travel ofthe magnetic element along the grooves.